Generally, a cigarette is a rod of cut tobacco wrapped in wrapping paper, where the opposite sides of the wrapping paper are stuck together with seam glue. In order to improve the taste of such cigarettes, it is known to add a flavoring material to cut tobacco. Recently, adding a flavoring material to seam glue in advance has been proposed (see Japanese Examined Patent Publication No. hei 6-95921, for example).
It is thinkable to apply a flavoring material onto cigarette wrapping paper instead of adding a flavoring material to cut tobacco or seam glue. A flavoring material is applied onto cigarette wrapping paper to improve the taste of cigarettes and/or suppress the odor of sidestream smoke. It is to be noted that in order to obtain a good taste of cigarettes by applying a flavoring material onto wrapping paper, the amount of the flavoring material applied onto the wrapping paper needs to be adjusted. In particular, when an odor-eliminating flavoring material capable of suppressing the odor of sidestream smoke is applied onto wrapping paper, the amount of the flavoring material applied needs to be adjusted more finely. Further, cigarettes made using that part of wrapping paper on which too small or too large an amount of a flavoring material is applied needs to be removed as defective products. In order to control the operation of a flavoring-material application device and a defective-product removal device to finely adjust the amount of a flavoring material applied and remove defective products, it is important to properly determine an applying state of the flavoring material applied on wrapping paper, as control information. It is however difficult to determine the applying state of the flavoring material.
Specifically, most flavoring materials are colorless, and therefore it is very difficult to determine the applying state of a flavoring material applied on wrapping paper through visual observation. Japanese Unexamined Patent Publication No. hei 4-34348 discloses a device for detecting defects due to non-uniformity of a sheet or the like such as a paper sheet or a polymeric film, using fluorescence radiated from a fluorescent substance. The principle of this inspection is that if a sheet or the like containing a fluorescent substance has structural non-uniformity in its surface or interior, light excited by the fluorescent reaction when the sheet or the like is illuminated by ultraviolet light is non-uniform. This non-uniform light is detected as indicating the existence of defects.
It is thinkable to apply such fluorescent reaction to the inspection on a flavoring material applied on cigarette wrapping paper. Specifically, it is thinkable to cast ultraviolet light onto wrapping paper on which a flavoring material containing a fluorescent substance or with a fluorescent substance added is applied, to cause fluorescence irradiation, and to determine an applying state of the flavoring material applied, by detecting the radiated fluorescence.
However, even if fluorescence radiated from a fluorescent substance contained in the flavoring material when illuminated by ultraviolet light can be detected, it only makes it possible to identify a region of wrapping paper in which the flavoring material is applied and determine whether or not there are defects in that region. It is difficult to inspect an applying state of the flavoring material applied, precisely enough to determine whether cigarettes are defective or not.